Telephone trunk-circuit.



,No. 657,3l6. Patented Sept. 4, I900. .D. S. HULFISH. TELEPHONE TRUNK CIRCUIT.

(Application filed m 25, 1900.)

(No Model.)

INVENTOR.

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UNITED STATES PATENT OFFICE DAVID S. HULFISH, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE AMERICAN BELL TELEPHONE COMPANY,

OF BOSTON, MASSACHUSETTS.

TELEPHONE TRUNK-CIRCUIT.

ssmmclmon formingpart of Letters Patent No. 657,316, dated September 4, 1900.

Application filed May 25, 1900.

To all whom it may concern.-

Be it known that 1, DAVID S. HULrIsH, residing at Chicago, in the county of Cook and State of Illinois, have invented certain Improvements in Telephone Trunk-Circuits, of which the following is a specification.

The present invention relates to telephone trunk-circuits, and especially to the automatic operation of the visual signals employed therewith to instruct the operators in charge at the several switchboard-sections as to the various changes taking place in the trunkcircuit or in the circuits connected thereto during the organization or disorganization of a main circuit for conversational purposes.

The purpose of theinvention is to provide a trunk-circuit with one visual signal located at the switching-plug terminal thereof, which is adapted to automatically operate, first, as a connection-signal when a connection-plug is inserted in the spring-socket terminal of the circuit, and, second, to automatically opbusy-test conditions to and from the operators telephone at the switchin g-plu g terminal.

In carrying out the invention means (as a plug-connector) are provided, when a call is made for a station which necessitates the use of a trunk-circuit for connecting the calling circuit with the switch-socket of the trunkcircuit, which causes a lamp signal to be lighted at the opposite or plug end of the said circuit to attract the attention of the switching operator there, who, after taking the call over an order-circuit, inserts the plug-terminal connector of the trunk-circu'itinto the switch-socket of the called-for circuit. The insertion of the plugconnector into the switch-Socket of the called-for circuit operates to efface or extinguish the lamp-signal, and upon the termination of the use of the circuit thus organized and the withdrawal of the plug-connector from the trunk-circuit switch-socket the same lamp-signal is again lighted or displayed to indicate to theswitching operator this time that a disconnection is desired. When the switching operator is notified of the circuit wanted over the order- Serial No. 17 981. (No model.)

circuit, she proceeds to make a test to ascertain whether the circuit is in use ornot, which is done in the usual manner, and at this stage of the circuit arrangement her telephone is in circuit with the tip of the trunk-plug; but when said plug is inserted in the switchsocket of the called-for circuit the telephone is automatically switched out of circuit.

Referring to the diagram which illustrates the invention, L is a trunk-circuit extending between the telephone-stations X and Y, and P at the former station represents one of a pair of switch-plugs A employed for connecting two circuits together, of which 1 and 2 are the conductor-cords connected, respectively, to the front sleeve contact-surface b and to the tip contact-surface a the rear contact-surface 0 being grounded by the wire 3.

Thetrunk-circuit L consists of three conductors 4:, 5, and 6, joined at station A to the springs a b and the test-ring a, respectively, of the spring-socket J. While at the station Y the conductor 4 terminates at the front contact-surface a of the plug P, the conductor 5 extends to the tip contact-surface b of said plug, while the conductor 6 is grounded through the windings of relay R and battery B. The rear sleeve contact-surface c of said plug is grounded through the conductor 8, the windings of relay R and battery B. The relay R is provided witharmatures f and g, one at each end of the core, the rear contact 10 of the armature f is connected to point It on conductor 6 by the wire .7, and the conductor 17 connects the said armature with point It on the conductor 8 andincludes in its circuit the visual lamp-signal S, and the rear contact 16 of armature g connects with conductor 5 at the point t by means of the conductor 9, while the armature is grounded through the operators telephone T by the conductor 15. V

L represents a substation or other circuit provided with one or more switch-sockets J adapted to .be connected by the plug P to the trunk-circuit L, and its conductors are at the socket J provided with the normally-open contact springs a and b and the test-ring c grounded by the conductor 18 through the resistance r.

In the operation of the invention, the operator at station A, having received a call requiring connection with a substation-circuit beyond her reach or with one whose terminal switch-socket is not upon her switchboardsection, but whichis located upon theswitch? board-section of the switching operator at switchboard or'station Y, and having upo'n-i her section the switch-socket J of the trunk-; circuit L, which may be multiplied to other operators switchboard-sections, proceeds to insert the calling-plug P of a-pair of switching cords and plugs into the switch-socket J, its conductors'l and 2 making connection with conductors "4 and 5, "respectively, andthe rear contact-surface c completing a"c ir-, cuit with the test-ring c, and current flows from battery B, conductors l4 and 17, lampsignal S, armature fof relay R conductors 7, I 6,"and 3 to grounds G and G and the lampsignalis lighted. At the same time currentfiows frolnbattery B, conductor 6, and winding of relay R to ground G, energizing the re-; lay and causing the attraction of armature e, which remains attracted while the plug P is'in the socket J. The switching operator at 'Yin response to the signallistens into an order-' circuit (not shown) and receiving the call for a connection of the, trunk-circuit with substation circuit L first touches the tip of plngi P to the test-ring c of switch-socket J and a circuit is completed from gronnd'Gi, cone ductor, 15, telephone T, armature g of relay I Iii-conductors 9 and 5, tip 6 of pin-grates;

ring c3,,conductor 18, and resistance r'toi ground G and if there is noconnectionat' another switching switchboard-section there will be no clicka in theutelephone, and con-y verselyfwhereupon she pushes thetplnginto the switch-socket, and the conductors 4 andi 5 are in electrical circuit with the conductors? of the circuit'L and the rear contact-surface joining the test-ring c -completes axcir'cuitl fromfbatterygB, conductor 8, winding of rea v v I arm'atures f andg, from their backer resting:

lay R conductor- 18"to;gronnds G4 and Gtf and the relayis energized andattracts its,

contacts 10 and 16, and anunobstructed talk:

" .ing-circuit is providedbetween section's X;

II 'andY. The ,-plugiP at 'thevtermination of j 5 I I socket J ,therebyopeningthe circuit through;

conversation is-withdrawn -from the switch};

. V rel'ayR and battery, and the armature train; upon its. resting-contact 14 and a icircnitiis,

completed from'battery B,conductor I7,lanip- I signal S, armature f of relay Ra it siforwardi contact 11,1'conductor "12, armature -e,-and,- conductor 13 toground G ,and the laxnp signallightsto indicate to the switching op,-

lerator Ta disconnection, and she then with- I 66' l andithe circuitsresume their normal c0ndi I tion. There will be no confusionin'thqmind draws'theplugP 'from the switch-socket J of the operator when the :lamp is ilight'ed as to whethenit is for a conneetionor discon-i nectiousignal, as shewill' be aware o'f-theI position of the plug P whether itis upon the;

keyboard or within-a switch socketfJt- The relative proportions of the apparatus employed depend largely upon the potential resistance as to operate upon the full voltage of the battery, and with such a battery the relay'R may be of forty ohms resistance and I that of relay R about ten ohms, and the re sistance-coil r is arranged for the substationcircuit L and therefore forms no part of the proportions of I my invention, but varies from lthirty to forty-five ohms, according to the special kind of circuit, and therefore accords very well with the dimensions hereingiven for the ,trunkcircu'i't.

I 1. In a telephone-exchange apparatus, the combination with a 't-runk circuit extending between two s witching-stationsand provided at each with switch devices; of an independent signaling-circuit normally open at both relays controlled by the said switchdevices at the two'switchingrstationsadapted to be operated serially by the said switch devices to, ,first, complete a circuit through-one relay and the source of current'and sim ultaneously therewith completef'afsecond circuit through the source of current and' cause-the display of said signal; andsecond, to completea circuit through the second relay'and the source of current andopen the signal-circuit,;asset forth, I I I III 2. In a telephone-exchange.apparatus, the

combination with a trunk-circuit extending betweentwo switchingstationsiand; provided at each with switchdevices; of anindependent.signaling-eircuit normally open at both stations, vcomprising a visual signal, a source ofLs i-gnalin -current',,and two circuit-closing relays controlled by the said switch devices atthetwo switching-stations; {and a busy test circuit normally closed by one ofsaidrelays thesaid relays adapted to be operated serially by'thelsaid: switch deviceslto', first, complete a'circuit through one relay and the source of current and simultaneously therewith completessecondcircuit through the source of current and causethe displayof said signal; and,.second,to completea circ uitthrough the second relay, and the source of current and opensignal-circuit and alsofthe testrcircuit, asset'forth. 'f I i In a telephone excha'nge, apparatus, the combination with a trunkmetallic circuit extending between-two switching-stations and provided at each end with switch devices; of an independent signaling-circuit normally openin the switch-socket andplug terminals of the trunk-circuit at thesaidstations com- ,prising al'single conductor branchingfirst through the windings of one relayto a'so urce stations, comprising a-visual signal, a source ,of'signalingcurrent, and two circuitclosing of current and ground, and second, through the switching-armature of a secoiid relay, a visual signal and the source of current to ground; the windings oi the second relay being in circuit with a contact-surface of the plug-terminal to ground throughthe source of current; and a test-circuit normally closed and grounded through the switching'armature of the second relay to the tip of theterminal plug, whereby when the switch-socket terminal is grounded the visual signal is lighted, and when the tip of the terminal plug is in touch with the test-ring of a telephone-circuit the test=circuit is completed, as set forth.

4:. In a telephone-exchange apparatus the combination with a trunk metallic circuit extending between two switching-stations and provided at each end with switch devices; an independent signaling-circuit normally open in the switch-socket and plug terminals of the trunk-circuit at the said stations, comprising a single conductor branching first through the windings of one relay to a source of current and ground, and second, through the switching-armature of a second relay a visual signal and the source of current to ground;

the winding of the secondrelay being in circuit with a contact-surface of the plug-terminal to ground through the source, of current; and a test-circuit normally closed and grounded through the switching-armature of the second relay to the tip of the terminal plug; whereby when the switch-socket terminal is grounded the visual signal is lighted, and when the circuit of the second relay is grounded at the plug-terminal the signal is extinguished, as set forth.

5. In a telephone-exchange apparatus the combination with a trunk metallic circuit eX tending between two switching-stations and provided at each end with switch devices; an independent signaling-circuit normally open in the switch-socket and plug terminals of the trunk-circuit at the said stations, comprising a single conductor branching first through the windings of one relay to a source of current and ground; and second through the switching-armature of a second relay, a visual signal and the source of current to ground;

the winding of the second relay being in cir-' cuit'with a contact-surface of the plug-ter minal to ground through the source of current; and a test-circuit normally closed and grounded through the switching-armature of the second relay to the tip of the terminal plug, whereby when the switch-socket terminal is grounded the visual signal is lighted, and when the circuit of the second relay is grounded at the plug-terminal the signal is extinguished, and when the ground is re= moved from the switch-socket terminal the visual signal is relighted, as set forth.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, this 20th day of May, 1900.

DAVID S. HULFISH.

Witnesses: BERNARD D. WILLIs, I

V J. B. MCMEER. 

